The present invention relates to a multi-mode imaging system and, more particularly, to an imaging system adapted to operate in a conventional document scanning mode or, alternatively, in a print mode, wherein an optical image is selectively addressed to produce a light output conforming to an image input pattern.
The versatility of document reproduction machines is enhanced when the machine is enabled to operate in an electronic print (WRITE) mode as well as the conventional document scan/illumination (COPY) mode, using optical components such as lenses and mirrors. Examples of prior art imaging systems which operate in more than one mode are disclosed in U.S. Pat. Nos. 4,345,835, 4,477,175, 4,527,886 and 4,194,833. The 835 patent discloses a system which uses a conventional document scanning system to expose a document at a photoreceptor and, in a second mode, uses a modulated laser beam to write an image onto the photoreceptor. The '886 patent discloses a multi-mode system which incorporates a moving platen to move a document past a fixed optical system in a copy mode. A second print mode of operation is enabled by positioning a liquid crystal assembly beneath the platen and directing a light output through the same optical system to form an image conforming to the state of the liquid crystal display. The '175 patent discloses a multi-function printer which utilizes a light lens system in a COPY mode and an array of addressable LEDs beneath the platen in a WRITE mode. The '833 patent discloses, as shown in FIG. 3, a copier operating with a movable platen in a COPY mode. In FIG. 2, the copier is shown operating in a WRITE mode wherein a liquid crystal shutter (LCS) is mounted on the document platen. The state of the display is controlled by inputs from an electronic typewriter. The LCD array is addressed through a plurality of cycles which being illuminated from beneath the platen by a high intensity lamp. The reflected light exposes the drum photoreceptor in sequential fashion.
These prior art systems, and other similar systems, have the disadvantage of either requiring relatively expensive laser systems to enable the WRITE function, or locate the printing assembly components in the optical housing space, thereby increasing overall space requirements. For the system shown in the '833 patent, the optical system lacks a linear projection means which adversely affects the quality of the image transmitted to the photoreceptor surface.
It would be desirable to provide a compact document reproduction machine which, besides being operable in a conventional COPY mode, is also operable in a WRITE mode. Ideally, the WRITE mode capability should not add significantly to the manufacturing cost of the machine, or to retrofit costs, in the case of an existing machine. Further, the WRITE capability should not increase the size of the optical assembly space used in the COPY mode and should result in optimum resolution and focus of the image at the photosensitve surface. The present invention is therefore directed to a multi-mode imaging system for a document reproduction machine which, in a conventional COPY mode, provides relative scanning motion between a document on a platen and an optical system for producing an exposed image at a photoreceptor surface. The system has a further WRITE mode capability enabled by positioning an image bar over or within the platen and in optical alignment with a linear lens array. The image bar, in a first embodiment, is a light emitting diode (LED) array partially positioned within the body of the platen or, alternatively, disposed on the top surface of the platen. In another embodiment the image bar can be an LED or a liquid crystal shutter (LCS) assembly, each respectively positioned in optical alignment with the lens upon initiation of the WRITE mode. More particularly, the invention relates to a multi-mode document imaging system having a first document COPY mode and a second document WRITE mode, said machine comprising:
a transparent platen lying in an object plane for supporting a document in a COPY mode, PA1 a linear lens array disposed between the platen and a photosensitive image member, PA1 an optical assembly for scanning a document in the COPY mode, said assembly including an elongated illumination source for incrementally illuminating a scan strip extending across the platen width, PA1 a linear image bar disposed within the object plane and in optical alignment with said lens array during a WRITE mode, PA1 control means for providing relative movement between said platen and said optical assembly during a COPY mode so as to incrementally scan and illuminate a document placed on the surface of said platen, said control means further adapted to position and maintain said image bar in optical alignmet with said lens array upon initiation of, and during said WRITE mode, and PA1 an electrical signal source enabled during the WRITE mode, for providing input signals corresponding to a desired output image to said image bar whereby said image bar output is coupled into said lens array and projected onto said photosensitve member, forming a latent image thereon.